Resealable safety valve

ABSTRACT

An integral low profile cell closure equipped with resealable safety valve means is disclosed having a cover, an apertured seat centrally enclosed within the cover, elongated resilient sealing means bearing on the seat, and a top cover bearing on the resilient means at a position outwardly spaced from the bearing positions formed with the seat. The cover and top cover are secured together at their respective marginal portions, effected by crimping the cover around the top cover, for instance, to provide a large cross-sectional escape path for gas released through the valve.

United States Patent Stark et al.

[451 Dec. 19, 1972 [54] RESEALABLE SAFETY VALVE [72] Inventors: Robert E. Stark, Littleton; Toshio Uba, Denver, both of Colo.

[73] Assignee: The Gates Rubber Company,

Denver, C010.

[22] Filed: Nov. 23, 1970 [21] Appl. No.: 92,100

[52] US. Cl. ..136/178, 215/56, 220/44 [51] Int. Cl. ..H0lm l/06 [58] Field of Search ..136/178; 220/44; 215/56 [56] References Cited v UNITED STATES PATENTS 1,950,327 3/1934 Runte ..220/44 2,027,137 1/1936 Yeomans ..220/44 2,558,654 6/1951 Kendall et al. ...l36/l78 2,790,570 4/1957 Hodges et al ..215/56 2,953,272 9/1960 Mumford et al ..215/56 Primary Examiner-Winston A. Douglas Assistant ExaminerH. A. Feeley Att0rneyRaymond Fink, H. W. Oberg, Jr. and Curtis H. Castleman, Jr.

[57] ABSTRACT An integral low profile cell closure equipped with resealable safety valve means is disclosed having a cover, an apertured seat centrally enclosed within the cover, elongated resilient sealing means bearing on the seat, and a top cover bearing on the resilient means at a position outwardly spaced from the bearing positions formedwith the seat. The cover and top cover are secured together at their respective marginal portions, effected by crimping the cover around the top cover, for instance, to provide a large cross-sectional escape path for gas released through the valve.

1 1 Claims, 6 Drawing Figures PA'TEN'TEDutm I972 3,706,617

sum 1 or 3 FIG. I

INVENTORS ROBERT E. STARK TOSHIO UBA BY imz;

PATENTED I973 3 7 O6, 6 1 7 sum z are v FIG. 2# 28 2 28 22 FIG. 6

INVENTORS ROBERT E. STARK TOSHIO UBA RESEALABLE SAFETY VALVE BACKGROUND OF THE INVENTION This invention relates to safety relief valves for cell containers, such as battery cell containers which may develop excessive internal gas pressure.

While a number of safety valves are presently known which have the capability of automatically resealing upon venting of gas above a predetermined pressure, these safety valves have generally been deficientin a number of aspects. One disadvantage is the relatively high profile button which is conventionallyused to house the valve mechanism. Since battery cells are con structed of standard length, the width or height of the safety valve mechanism detracts from the available volume for active cell contents to be incorporated in the cell, thus decreasing the cells energy density and discharge capacity. Another drawback with conventional safety relief means is their propensity to vent at pressures other than thedesired pressur'e, i.e., they are unreliable. Prior art constructions in which the resilient sealing means is urged downwardly by a top cover at bearing positions approximately directly above the bearing positions between the resilient member and seat cover usually prevent repeatable gas relief at the desired predetermined pressure, or within a desired tolerance thereof. In fact, these safety relief means often vent at internal pressure values widely differing from the desired predetermined pressure value. Another drawback with normal safety valve configurations is that the provided path for gas escape is usually a single vent port, or merely a plurality of ports. Particularly in alkaline cells, entrained electrolyte often is trapped within the port and reacts with carbon dioxide present in the atmosphere to form crystalline potassium carbonate which plugs or severely restricts the avenue of escape for the vented gas. Furthermore, these conventional button caps are secured to the cell cover by a plurality of spot welds which increase manufacturing costs and render the cell top aesthetically unattractive.

Pertinent prior art may be found in United States Patent Office Classification Class 136, Batteries, and Class 215, Bottles and Jars. Specific relevant references include U. S. Pat. Nos. 2,790,570, 3,293,081, 3,484,330] and 3,5 16,870.

Among the objects of the present invention is to maximize the cell discharge capacity by minimizing the height of the cell top closure, which includes the resealable safety valve of the present invention. Another object is to provide a maximum area or path cross section for egress of vented gas about the periphery of the top closure. It is another object to provide a reliable seal which will vent at a predetermined pressure within a close tolerance level.

These and other objects of the invention are met, and the disadvantages of the prior art overcome by employing the construction of the present invention as herein. disclosed.

SUMMARY OF THE INVENTION Briefly described, the invention comprises a low profile top closure for a battery cell container equipped with a resealable safety valve, and comprising a cell cover heaving an apertured seat, a resilient means positioned over the aperture and bearing on the seat, and a cell top marginally engaged to the cell cover, bearing against the resilient means and urging the same against the seat. Reliability of venting within a small tolerance of the desired venting pressure is provided by means of a relatively thin resilient member which extends well beyond the seat and bears a against the cell top cover outwardly away from the position at which the resilient means bears against the seat. A-large escape path for vented gas is provided at the marginal portions of the top cover and cell cover.

The safety valve closure of the present invention has wide use in battery closure construction, particularlyin' conjunction with alkaline cells, although the invention broadly pertains to a varietyv of cell closures where a resealable safety valve mechanism is required.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, FIG. 1 depicts schematically in section the top closure of the present invention, showing its relative position with respect to the top portion of a cell container and insulating sealing means;

FIG. 2 is a view of the resilient means used to bias the cell in a normally sealed position;

FIG. 3 depicts in section a modified means for gas escape;

FIG. 4-is a sectional view showing another modified method for facilitating gas escape;

FIG. 5 illustrates in section the resilient means; andv FIG. 6 shows an exploded view of the top closure of FIG. 1.

PREFERRED EMBODIMENTS OF THE INVENTION The invention will be more fully described by reference to the accompanying drawings which depict preferred, but non-limiting embodiments of the invention.

In FIG.1, an empty cylindrical battery container 10 is shown carrying the top closure of the presentinvenuse of an alternative tion insulatingly disposed bysealing ring 12. The top closure consists of elongated cover 14 which has a raised annular seat 16 in which is disposed aperture 18 in fluid communication with the interior 20 of the battery cell. A resilient means generally designated at 24 is positioned over the aperture 18 and bears against the surface of seat 16. The resilient means 24 is comprised of resilient material 22 having a coating 26 on its bottom surface. A metal disk, metal leaf spring, suitable plastic material such as polyimide, polysulfone, and other resilient materials having low cold flow, are examples of suitable resilient materials. The coating material is preferably elastomeric in nature to maintain the desired seal. Furthermore, the coating should be resistant to degradation by cell fluids such as electrolyte of the battery cell, in which the coating may come into contact. Examples of such materials include neoprene, Buna-N rubber, certain latices, I-lycar, other natural and artificial rubbers and the like. The coating or layer 26 may be conventionally secured to the resilient material, such as by lamination.

As shown more particularly in FIG. 2, leaf spring 22 may consist of a plurality of fingers, every other one of which is bent downwardly 28 to permit self positioning of the resilient means 24 on the seat 16. Of course, the leaf spring 22 may be any desired configuration so long as it is substantially thin and extends approximately horizontally across the seat, extending peripherally well beyond the seat. Examples of other configurations include a disk coated 26 on its entire bottom surface and an eight-fingered leaf spring. The particular embodiment or design of cell closure will suggest to those skilled in the art various designs for the resilient means 24.

Referring again to FIG. 1, at least a portion of the upper surface of resilient means 24 bears against top cover 30 at bearing points or surface 32. It is one feature of this invention that the position 32 at which the top cover 30 bears against the resilient means 24 is spaced outwardly from the surface 'at which seat 16 and elastomeric layer 26 come in contact. This spaced bearing arrangement provides a low profile top closure and further greatly improves the reliability of the seal by lowering the tolerance range from the predetermined value at which the gas pressure should release from the interior 20 of the cell. For ease of illustration, an exploded view of the entire top closure of FIG. 1 is shown in FIG. 6. The parts are assembled as shown. The leaf spring 22 laminated with elastomeric disk 26 is placed upon seat 16. The spring is biased against the seat with cover 30 by crimping cover wall 34 about the peripheral portion of top cover 30.

In FIG. 5 a modification of the invention is depicted in which resilient means 24 is comprised of a single elastomeric diaphragm (resistant to cell fluids) stretched across seat 16 having annular upstanding projection l7, and secured between cover 14 and top cover 30 at a plurality of positions 15. The diaphragm 24 should not be continuously crimped at '15 around the. top closure since this would prevent an avenue or path for gas exit.

It is one feature of this invention that the angle formed between the horizontal extension of the seat bearing portion of resilient means 24 and the extending peripheral edges 33 of the leaf spring be preferably no greater than 37 and more preferably no greater than and most preferably no greater than about 8, the angle being designated 0 as depicted in FIG. 1. In the case where the extending edge 33 is curved, the angle 0 is defined using the tangent constructed at the bearing contact point.

In operation of the invention, a particular resilient means 24 is chosen to allow venting at a predetermined pressure. The size of the aperture 18 and stiffness of the resilient means 24 are chosen to allow venting at the predetermined pressure. Excessive gas pressure buildup within the interior 20 of the cell above the predetermined value urges the elastomeric coated leaf spring 24 away from seat 16 allowing gas to enter free space 36 and around the peripheral portion 38 of top cover and into the atmosphere. The valve closes automatically once the internal pressure drops below the predetermined pressure value. It has been found that the mere crimping of walls 34 about top cover 30 do not form such a contiguous sealing relationship therebetween to prevent copious escape of gas when the cell has developed the predetermined internal pressure. Alternatively, as shown in FIG. 3, escapa ge of gas may be facilitated by upper slots or grooves 40 and lower slots or grooves 42 coined in the covers peripheral portion 38. Similarly, as shown in FIG. 4,

peripheral portion 38 may be provided with a plurality of bosses 44 or other type of upstanding projections at approximately its peripheral edge.

It should be understood that the invention-is capable of a variety of modifications and variationswhich will be made apparent to those skilled in the art upon a reading of the instant description and which are meant to be included within the scope of the invention as claimed. One such modification would be to employ means, e'.g. in the form of slots, grooves or embossments, may be provided along the peripheral portion of cover 14 in lieu of or in addition to the depicted means in FIGS. 3 and 4.

What is claimed is: 1. In an electrochemical cell having a container and a top closure fitting in the end of said container and equipped with a normally sealed safety valve, an improved top closure of low profile comprising:

a. a first cover having a seat and an aperture therein in fluid communication with the interior of said cell, said first cover in marginal insulative sealing engagement with said container;

. a second cover'urging downwardly upon and marginally engaging said first cover, said second cover having the general shape of an inverted dish comprising an annular inclined side portion and an annular marginal flange portion joining and extending outwardly from said inclined side portion; and

. elongated resilient sealing means having a central portion bearing on said seat and having marginal portions radially spaced outwardly from said seat and contacting only said second cover, said contact occurring at the approximate juncture of said inclined side portion with said marginal flange portion of the second cover, the angle formed between the horizontal extension of the central portion of said resilient sealing means and the being no greater than about 37.

2. The cell of claim 1 wherein the marginal portions of said first cover are crimped aroundthe marginal portion of said second cover to define a continuous gas escape exit at the periphery of said top closure.

3. The cell of claim 1 wherein the resilient means includes means for self-positioning upon said seat.

4. The cell of claim 1 wherein the resilient means comprises a metal leaf spring having on its bottom side an elastomeric material adapted to engage the seat.

5. The cell of claim 1 wherein the resilient means comprises a resilient plastic material of low cold flow coated on at least a portion of its bottom side with an elastomeric material adapted to engage the seat.

6. The cell of claim 1 wherein the peripheral portion of the first or second cover surface is slotted or grooved at a plurality of locations to enhance gas escape therethrough.

7. The cell of claim 1 wherein the peripheral portion of the first or second cover surface is provided with upstanding projections to enhance gas escape therethrough.

8. The cell of claim 3 wherein the self-positioning means comprises a plurality of fingers some of which are bent downwardly, for positioning about the seat.

9. The cell of claim 1 wherein the angle formed between the horizontal extension of the central portion of the resilient means and the peripheral extension of the marginal portions of the resilient means beyond the seat is less than about 25.

' 10. The cell of claim 1 wherein the angle formed 

1. In an electrochemical cell having a container and a top closure fitting in the end of said container and equipped with a normally sealed safety valve, an improved top closure of low profile comprising: a. a first cover having a seat and an aperture therein in fluid communication with the interior of said cell, said first cover in marginal insulative sealing engagement with said container; b. a second cover urging downwardly upon and marginally engaging said first cover, said second cover having the general shape of an inverted dish comprising an annular inclined side portion and an annular marginal flange portion joining and extending outwardly from said inclined side portion; and c. elongated resilient sealing means having a central portion bearing on said seat and having marginal portions radially spaced outwardly from said seat and contacting only said second cover, said contact occurring at the approximate juncture of said inclined side portion with said marginal flange portion of the second cover, the angle formed between the horizontal extension of the central portion of said resilient sealing means and the being no greater than about 37* .
 2. The cell of claim 1 wherein the marginal portions of said first cover are crimped around the marginal portion of said second cover to define a continuous gas escape exit at the periphery of said top closure.
 3. The cell of claim 1 wherein the resilient means includes means for self-positioning upon said seat.
 4. The cell of claim 1 wherein the resilient means comprises a metal leaf spring having on its bottom side an elastomeric material adapted to engage the seat.
 5. The cell of claim 1 wherein the resilient means comprises a resilient plastic material of low cold flow coated on at least a portion of its bottom side with an elastomeric material adapted to engage the seat.
 6. The cell of claim 1 wherein the peripheral portion of the first or second cover surface is slotted or grooved at a plurality of locations to enhance gas escape therethrough.
 7. The cell of claim 1 wherein the peripheral portion of the first or second cover surface is provided with upstanding projections to enhance gas escape therethrough.
 8. The cell of claim 3 wherein the self-positioning means comprises a plurality of fingers some of which are bent downwardly, for positioning about the seat.
 9. The cell of claim 1 wherein the angle formed between the horizontal extension of the central portion of the resilient means and the peripheral extension of the marginal portions of the resilient means beyond the seat is less than about 25* .
 10. The cell of claim 1 wherein the angle formed between the horizontal extension of the central portion of the resilient means and the peripheral extension of the marginal portions of the resilient means beyond the seat is less than about 8*.
 11. The cell of claim 1 wherein the peripheral venting path formed between the marginal portions of said first and second covers lies substantially continuously around the perimeter of said second cover. 